Soaring temps cause mass coral killing in Indonesia: study

Coral reefs are suffering widespread damage in what is set to be one of the worst years ever for the delicate and beautiful habitats. A dramatic spike in ocean temperatures off Indonesia's Aceh province has killed large areas of coral and scientists fear the event could be much larger than first thought and one of the worst in the region's history.

The phenomenon, known as coral bleaching because the reefs turn bone white when the colorful algae that give the coral its color and food is lost, has been reported throughout south east Asia, the Indian Ocean and the Pacific.

High ocean temperatures this year are being blamed for the bleaching, which experts fear could be worse than a similar event in 1998 which saw an estimated 16 per cent of the world’s reefs being destroyed.

The coral bleaching -- whitening due to heat driving out the algae living within the coral tissues -- was first reported in May after a surge in temperatures across the Andaman Sea from the northern tip of Sumatra island to Thailand and Myanmar.

Divers and scientists have described huge areas of previously pristine reef being turned into barren white undersea landscapes off the coast of Thailand and Indonesia. An international team of scientists studying the bleaching event found that 80 percent of some species have died since the initial assessment in May.

More coral colonies were expected to die within the next few months and that could spell disaster for local communities reliant on the reefs for food and money from tourism.

Corals are a delicate combination of animal, algae and rock that form intricate undersea structures, providing shelter for thousands of brightly colored fish and also acting as nurseries for the young of many larger open sea fish. (At right: top reflects unbleached coral while bottom picture reflects bleached coral)

Coral reefs provide refuge and food to nearly a quarter of all marine species, making them among the most biologically diverse habitats on the planet. Bleaching can also rob fish and other species of important shelter and food sources.

"I would predict that what we're seeing in Aceh, which is extraordinary, that similar mortality rates are occurring right the way through the Andaman Sea," said Andrew Baird of James Cook University in Townsville, in the Australian state of Queensland.

If so, that would make it the worst bleaching recorded in the region, said Baird.

Scientists from the Wildlife Conservation Society and Syiah Kuala University in Aceh have also been assessing the damage. "This one of the most rapid and severe coral mortality events ever recorded," the U.S.-based WCS said in a statement.

It also fits a pattern of climate extremes, from heatwaves to flooding, that have hit many areas of the globe this year. Between April and late May, sea surface temperatures in the Andaman Sea rose to 34 degrees Celsius or about 4 degrees C above the long-term average, according to the U.S. National Oceanic and Atmospheric Administration's Coral Hotspots website.

SLOW RECOVERY

"Similar mass bleaching events in 2010 have now been recorded in Sri Lanka, Thailand, Malaysia and many parts of Indonesia," the WCS statement said.

Baird, of James Cook University's ARC Center of Excellence for Coral Reef Studies, stated that climate change could have played a role in the extreme ocean temperatures around Aceh.

"There might be one of these cyclic climate phenomena driving it but it's much more severe than you would predict unless there was something else forcing it, which is almost certainly global warming," he said on Tuesday.

The bleaching is a blow to local communities in Aceh still recovering from the 2004 tsunami. That disaster caused relatively little damage to reefs and Baird said some areas had showed a dramatic recovery.

Although reefs can often recover from bleaching, it leaves the coral vulnerable to damage from storms, infections and other environmental stress, increasing the risk of deaths.

Baird said reefs in Indonesia would normally take 5 to 10 years to recover from localized bleaching. But if the event was spread across a much wider area, recovery would take longer.

"I suspect the scale of this event is so large there is unlikely to be many healthy reefs in the rest of Aceh."

Coral Bleaching Study of the Great Barrier Reef

The Great Barrier Reef's (right) dominant coral species are among the most vulnerable to the effects of global warming according to a new research study.

A groundbreaking study into the immunity of coral species has found the iconic Acroporidae family to be among the most susceptible to outbreaks of disease or bleaching.

Acroporidae, also known as "reef building" coral for its role in the development of reefs, is among the most prevalent found in the Great Barrier Reef.

The branched structure and size of Acroporidae colonies (left) makes it among the most recognizable coral species in the world.

The study by scientists from James Cook University and the Australian Research Center ranked 17 coral species found on the reef according to their immunity.

It found species from the Acroporidae and Pocilloporidae (right) families ranked at the bottom of the scale, putting them at the most risk of bleaching or disease - both of which have been linked to global warming.

However, study leader Caroline Palmer said the Acroporidae corals were also among the fastest growing and most abundant species. They were, therefore, the most likely to survive as a species, even if individual colonies die.

"When a mass bleaching event hits they are one of the most affected species of coral but they seem to be bouncing back in a lot of places," she said. "They can reproduced faster so that when they are knocked back they can grow back a lot faster."

She said immunity levels appeared to be linked to the amount of energy a species assigned to it. Some, like the Acroporidae, (left) directed more energy towards growth reproduction, while other species had a slower growth rate but higher levels of immunity.

Source:
Reuters, "Soaring temps cause mass coral killing in Indonesia: study", accessed August 17, 2010
The Sydney Morning Herald, "Iconic coral species the most vulnerable", accessed August 17, 2010
Aquamarine Blog, "Coral reefs suffer mass bleaching", accessed August 17, 2010